1. Technical Field
Example embodiments of the present invention relate in general to a method of packetizing symbols and an apparatus using the same, and more particularly, to a method of packetizing encoded symbols and an apparatus using the same.
2. Related Art
In fields of studying networks and video coding, video streaming technology is important. There is a problem in that it is difficult to transmit video streaming traffic in an actual network environment because a video not only has a large amount of data, but also requires quality of service (QoS) of data.
It is essential to use an effective video compression algorithm so as to reduce a volume of video data in video streaming.
Heretofore, digital video coding technology for an effective video compression algorithm has been rapidly developing. International standards such as Moving Picture Experts Group (MPEG)-1, 2, and 4, H.261, H.263/+/++, and H.264 have been proposed to satisfy various requirements of the International Organization for Standardization/International Electrotechnical Commission (ISO/IEC) and International Telecommunication Union-Telecommunication Standardization Sector (ITU-T). Compressed video data has various bit rates because of entropy encoder characteristics, video scene changes, and irregular motion variations. Transmission errors and loss occur more easily in video data compressed at a high compression rate than in video data compressed at a low compression rate.
A problem to be solved is to effectively provide high-quality stable video streaming service in a wireless network.
Path loss, fading, multipath, and interference in video data transmission lead to an irregular variation in a signal-to-noise ratio (SNR) of video data received in a radio link.
It is difficult to decode a received signal at a low SNR, so that a bit error rate (BER) increases. An automatic repeat request (ARQ) and forward error correction (FEC) are widely used to reduce data transmission errors and loss in the wireless network.
In the ARQ, a delay increases because lost data should be retransmitted after feedback information is received. As an error prevention method, the ARQ may not be suitable for video streaming sensitive to a delay.
However, the FEC requires additional data for compensating for data loss and errors without requiring feedback information in the network. Characteristics of the FEC are suitable for video streaming sensitive to a delay, as compared to those of the ARQ method.
Fountain codes such as Luby transform (LT), raptor, and on-line codes are block-based FEC technology. Because the fountain codes have characteristics such as high coding efficiency, a short encoding/decoding processing time, and adaptability, the fountain codes are very useful in transmitting delay-sensitive data in an error-prone wireless network.
As rateless codes of channel coding, the fountain codes advantageously make error-free perfect reception possible only in one-way transmission when two-way information transmission is difficult as in the case where information regarding a reception end is insufficient in a side of a transmission end or the number of reception ends is very large.
Previously, the fountain codes have been studied for an erasure channel and actively applied to other channels. The erasure channel is a channel of which information is erased at a predetermined probability, regardless of transmitted information, and on which what is transmitted is not recognizable. Although the erasure channel has only been recognized as a theoretical virtual channel, the erasure channel has recently received attention as a channel capable of modeling the Internet with the development of the Internet.
Because an application is made only in the case where packets are accurately transmitted on the Internet or accurately received or discarded at a predetermined probability, regardless of which packet is transmitted, an Internet channel environment may be modeled as an erasure channel.
The standardization of the fountain codes is being studied in various fields. Until now, raptor codes from 2005 have been adopted in a channel encoding algorithm for standard broadcasting used in 3rd Generation Partnership Project (3GPP) Technical Specification (TS) 26.346 multimedia broadcast/multicast service (MBMS) and digital video broadcasting-handheld (DVB-H) Internet protocol (IP) datacast. Raptor codes used in a standard are defined to have systematic characteristics. In a pre-coding process, LT decoding is used to implement raptor codes having the above-described characteristics in 3GPP MBMS and DVB-H. That is, existing source symbols are assumed as symbols encoded by the same source symbol selection pattern as that of LT code parts of raptor codes. Accordingly, if a middle-step symbol obtained by LT decoding is LT-encoded, a source symbol may be directly included within an encoded symbol to be transmitted.
The fountain codes are also suitable for communication on a wired network because the fountain codes are basically designed to operate in the erasure channel. Also, in wireless communication, the fountain codes may be regarded as in the erasure channel and applied because it is only determined whether or not a received packet is correct information by applying a cyclic redundancy check (CRC) on a medium access control (MAC) layer. As compared to hybrid ARQ (H-ARQ), which is another coding technique used in the MAC layer, the fountain codes have characteristics in that error-free information may be perfectly received in a reception end without an interaction between a transmission end and the reception end. Accordingly, the fountain codes may have an advantage as compared to an H-ARQ transmission technique in which communication is performed until information is perfectly received between two ends.
To provide a video streaming service, which stably satisfies QoS, packet loss should be minimized by reducing dependency between packets delivered to minimize data loss caused by the packet loss occurring in a wireless network. An LT decoding failure rate should be reduced with the same number of packets by estimating whether a sufficient number of encoded symbols may be transmitted in an error-prone wireless network.